1. Field of the Invention
The present invention relates to an integrated switch and a switching method for simultaneously processing IP data and voice signals, and more particularly, to an integrated switch and a switching method for simultaneously processing IP data and voice signals using silent periods during communication between a switch subscriber and a counterparty.
The integrated switch according to the present invention provides a function of transmitting data packets using the silent periods during the communication of an existing switch subscriber, so that an existing frequency band and apparatus can be used without use of a separate frequency band and a separate apparatus for data transmission such as an asymmetric digital subscriber line (ADSL). In addition, efficiency of an existing switch can be increased without use of an apparatus for collecting and processing data disposed in front of subscriber line cards.
2. Description of the Related Art
In general, during a communication period, a voice channel is not entirely filled with voice signals. That is, the communication periods can be divided into talk-spurt periods in which voice signals are generated and silent periods in which voice signals are not generated and voice information is not transmitted.
According to some research, it is reported that the talk-spurt periods in which voice signals are generated and voice information is transmitted occupies less than 50% of the total communication period (refer to an article, “A study of on-off characteristics of conventional speech”, H. H. Lee & C. K. Un, pp 630-637, IEEE Trans. on Comm., Vol. COM-34, No. 6, June 1986).
The International Telecommunication Union-Telecommunication (ITU) has standardized such characteristics of voice communication. Much research for transmitting different information during the silent periods of a voice communication channel has been conducted (refer to ITU-T Recommendation P. 59, “Telephone transmission quality objective measuring apparatus”, March, 1993).
As examples of technology for transmitting voice signals and data packets in a circuit switching network, traditional circuit switching, fast circuit switching, and enhanced circuit switching have been proposed, and their advantages and disadvantages have been analyzed (refer to an article, “Voice/data integration using circuit switched networks”, E. A. Harrington, pp 781-793, IEEE Trans. on Comm., Vol. COM-28, No. 6, June 1980).
According to the aforementioned document, when a gap between data and a message is relatively long, fast circuit switching is advantageous. When the gap is relatively short, traditional circuit switching is advantageous).
Enhanced circuit switching is introduced so as to enhance the two circuit switching schemes, that is, fast circuit switching and traditional circuit switching. In enhanced circuit switching, a common signal scheme is used. In addition, a time assigned speech interpolation (TASI) scheme is used for voice signal multiplexing, and an adaptive data multiplexing (ADM) scheme is used for data signal multiplexing.
According to a result of analysis of a circuit switching network using the enhanced circuit switching scheme, as the number of transmission channels between switch nodes is increased, different voice signals and data signals can be inserted in the silent periods. However, as the number of channels is small, the voice signals may be lost due to channel competition.
In addition, since paths of the data packets are handled directly by an internal portion of the switch, an increase in the number of channels leads to increased costs of switching.
U.S. Pat. No. 6,044,266 (Mar. 28, 2000) discloses a method of transmitting data in the silent periods of a mobile voice terminal in a wireless region. In the method, when the mobile voice terminal broadcasts information indicating that voice signals are not transmitted, a mobile data terminal measures an intensity of the signals of the mobile voice terminal to select the best channel and transmits the data with the same size of the signal of the mobile voice terminal in the silent periods.
According to U.S. Pat. No. 6,044,266, the communication channel can be used for transmitting data in the silent periods, that is, periods other than the talk-spurt periods in which the voice signals are transmitted, so that use efficiency of the voice channel can be increased.
However, the mobile voice terminal needs to inconveniently broadcast silent period information and to continuously measure intensities of output signals of neighboring mobile voice terminals. Therefore, the method is complicated and expensive.
In addition, in a case where a frequency hopping scheme is used due to security problems, the method cannot be directly used. The method can be used for only the wireless transmission region. Therefore, in an internal portion of the switch, the voice signals and the data need to be separately processed.
U.S. Pat. No. 7,095,759B1 (Aug. 22, 2006) discloses a statistical multiplexing method of processing voice signals and data signals at one time in a trunk for external connection of a private switch such as a private branch exchange (PRE).
In the statistical multiplexing method, the voice signals and the data signals are processed in one common resource (referred to as a pool). The statistical multiplexing method is based on a channel connection scheme. In addition, the statistical multiplexing method does not include a concept that the data is transmitted in a silent period.
US Patent Publication No. 2006/0239283 A1 (Oct. 26, 2006) discloses a statistical multiplexing control method of processing voice signals and data signals at one time in a private switch such as a private branch exchange (PBX). In this method, voice channels and data channels are processed as one common resource (pool).
The statistical multiplexing control method is also based on the channel connection scheme. In this method, packets are deleted according to priorities thereof, and the deleted packets are processed in upper layers. According to the method, a re-transmission request of the upper layer or the like may lead to deterioration in use efficiency of paths. In addition, the method does not include the concept that data is transmitted in silent periods.
U.S. Pat. No. 6,611,536 B1 (Aug. 26, 2003) discloses a method of transmitting voice signals together with data signals in a single RF channel. In the case of a plurality of channels, silent periods between the voice signals include silent gaps having a fixed length, and digital voice signals are transmitted in the silent gaps. For the transmission of the digital voice signals, data packets having a variable length are transmitted according to the silent gaps having the fixed length based on information of the silent gaps, which is obtained in advance.
In this method, a plurality of communication paths are needed. In addition, the method can be used only in the wireless transmission region excluding the switch.
Therefore, a technique is needed for processing voice signals together with data signals in an existing switch by transmitting data packets in silent periods in the same channel during communication without use of a separate frequency band and a separate apparatus for data transmission such as an existing ADSL for wire and wireless subscribers of the switch, capable of using the existing frequency band and apparatus without the need for an apparatus for collecting and processing data disposed in front of subscriber line cards.